The invention relates to electric heating members and particularly to such members as must necessarily be periodically exposed to hostile environmental conditions such as steam, hot water and chemicals. One example of such an environment is disclosed in Colato et al U.S. Pat. No. 4,005,745 where an institutional feeding apparatus is disclosed. The disclosed apparatus includes a cabinet-like cart whose interior is refrigerated and which contains a plurality of semi-permanently mounted heater plates which are adapted to heat food containers positioned on a food tray located immediately above each heater plate. The carts must be washed after each use with a steam or hot water spray and germicidal solutions. Where the heater plates are not perfectly sealed, moisture can get inside them where expansion and contraction with temperature changes can further harm the seals and cause short circuits in the heater elements.